Rock drill

ABSTRACT

A rock drill ( 1 ) with a helical thread ( 2 ) and a hard material insert ( 3, 9 ) in the drilling head, form a radically outer guiding surface ( 6 ), with the guiding edge ( 6 ) forming an acute angle (α) with the direction of the tool axis (A).

FIELD OF INVENTION

[0001] The invention relates to a rock drill for abrasively working rockor a similar hard material by a movement, which is at least a partiallyrotating and striking movement with respect to the axis of the drill,with a helical thread and a hard material insert in the drill head.

BACKGROUND INFORMATION AND PRIOR ART

[0002] Conventional rock drills have a hard material insert, formed as ahard material plate or as a solid hard material drilling head, which isfastened to the tool head, from which a shaft with a helical threadextends, and finally ends in a plug-in or chuck region for accommodationin a tool device.

[0003] For guiding the drill radially in the borehole, for decreasingthe vibrations and for producing an approximately circular borehole,rock drills with diameters of about 5 mm have main cutting edges as wellas subsidiary cutting edges, set at an angle to the main cutting edges.Generally, the main cutting edges as well as the subsidiary cuttingedges have blunt guiding surfaces, which are disposed at the radialperiphery and guide the tool head axially, in that they slide past theinner surface of the borehole. Such guiding surfaces, which causefriction, are dimensioned as small as possible.

[0004] According to the U.S. Pat. No. 5,553,682, a rock drill has asolid hard material head with two main cutting edges and two subsidiarycutting edges, the peripheral blunt guiding surfaces of which, extendingin each case parallel to the axis of the drill, change over intoquadruple helical threads. The guiding sector region in the crosssectional plane, which is only small and is guided with the guidingsurface of each cutting edge, is a disadvantage.

[0005] According to the DE 602663, a twist drill, for working materialsby cutting, has a tool head with two hard material plates, which formthe main cutting edges, and the peripheral, blunt guiding surfaces ofwhich change over into the quadruple helical threads. Moreover, theindividual hard material plates, and the guiding surfaces of whichcontinue the helical threads smoothly, are disposed at an angle to thedrill axis and are fastened to the tool head by, in each case, one ofthe side surfaces, and facing the drilling direction. As a result, theside surface is integrated in the end region of the helical grooves,which is highly stressed by the cutting operation. An axially strikingstress exerted on such a hard material insert would stress theattachment of this insert to the tool head, resulting in failure after ashort time.

SUMMARY OF THE INVENTION

[0006] It is an object of the invention to provide a rock drill with alarge guiding sector region in the cross sectional plane.

[0007] Essentially, in the case of a rock drill with a helical threadand a hard material insert, the fastening of which to the rest of thetool is designed for an at least partially rotating and striking stress,at least one guiding surface of a hard material insert is disposed at anacute angle to the direction of the tool axis.

[0008] By these means, the guiding sector region in the cross sectionalplane is enlarged approximately in proportion to the sine of the anglewithout increasing the friction-producing region of the guiding surface.

[0009] The hard material insert is fastened only over the surfaces ofthe insert, which face opposite to the drilling direction or at rightangles thereto. With that, the fastening is exclusively for compressionand shear stresses and will not fail due to impact stresses.

[0010] Advantageously, the guiding surface smoothly continues thehelical threads, as a result of which the resistance to conveying theexcavated material in the helical groove is reduced.

[0011] In a first advantageous embodiment, the rock drill has a solidhard material head, which is fastened at its surface facing opposite tothe drilling direction or oriented perpendicularly thereto. The guidingsurface edge of at least one hard material insert forms an acute anglewith the direction of the tool axis.

[0012] In a second advantageous embodiment, the rock drill has a hardmaterial plate, which is fastened with its surfaces, which face oppositethe drilling direction or oriented perpendicularly thereto. The guidingsurface of at least one hard material insert forms an acute angle withthe direction of the tool axis.

[0013] Advantageously, a hard material plate is fastened only along asurface, facing opposite to the drilling direction, to the remainder ofthe tool. Furthermore, preferably, a free surface facing in the drillingdirection is integrated smoothly into the highly abrasively stressed endregion of the helical grooves.

[0014] With the inventive solution, a large, hard material-faced,wear-resistant guiding sector can be realized in the cross sectionalplane with a small volume of hard material.

[0015] Due to the inclined guiding surface, the solid material head nolonger is completely prismatic. Advantageously, it is produced byinjection molding.

BRIEF DESCRIPTION ON THE DRAWINGS

[0016] The invention is explained in greater detail with respect to anadvantageous example in:

[0017]FIG. 1 is a axially extending side view of a drilling head end ofa first rock drill; and

[0018]FIG. 2 is a axially extending side view of a drilling head end ofa second rock drill.

DETAIL DESCRIPTION OF THE INVENTION

[0019] According to FIG. 1, a rock drill 1, with a quadruple helicalthread 2, has a solid hard material head which has main cutting edges 4and is mounted on the drilling head end of an axially extending shaft onwhich the helical threads 2 are formed. The peripherally extendingguiding surface 6 of a main cutting edge 4 forms an acute angle α, withthe direction of the shaft A, as a result of which, with respect to aparallel orientation, an enlargement of a guiding sector region 7 isachieved in the cross sectional plane. The solid hard material head 3 isfastened with its rear end surface 8, facing opposite to the drillingdirection, to the remainder of the tool. The guiding surface 6 smoothlycontinues the helical thread 2.

[0020] In FIG. 2, a double helical thread 2 has two hard material plates9, which form main cutting edges 4 of the drilling head and are disposedradially about a central cutting member 10. The radially outerperipheral guiding surface 6 of a main cutting edge 4 forms an acuteangle α with the direction of the tool axis A and smoothly continues thehelical thread 2. With its end surface 8, facing opposite to thedrilling direction, the hard plate 9 is fastened to the drilling headend of the tool. As a result, the free cutting surfaces 11 leading inthe drilling direction are integrated smoothly into the highlyabrasively stressed drilling end region of the helical grooves.

What is claimed is:
 1. A rock drill having a shaft with an axis (A),said shaft having a drilling head end with at least one helical thread(2) extending from said drilling head end, at least one hard materialinsert (3, 9) mounted on said drilling head end and designed forrotating and axially striking stresses, said insert (3, 9) having atleast one guiding surface (6) at a radially outer peripheral surface ofsaid drilling head end and said guiding surface (6) forms an acute anglewith said shaft axis.
 2. A rock drill, as set forth in claim 1, whereinsaid hard material insert (3, 9) is fastened only on a surface (8)facing one of opposite to a drilling direction of said rock drill andopposite to and extending perpendicularly to the drilling direction. 3.A rock drill, a set forth in claim 2, wherein said guiding surface (6)smoothly continues said helical thread (2).
 4. A rock drill, as setforth in claim 3, wherein said hard material insert (3, 9) is formed asa hard material head (3) with a drilling end facing in the drillingdirection and a trailing end secured to said shaft.
 5. A rock drill, asset forth in claim 3, wherein said hard material insert is formed as ahard material plate (9).
 6. A rock drill, as set forth in claim 5,wherein said hard material plate (9) is fastening only to said drillinghead end on a surface (8) facing opposite to the drilling direction. 7.A rock drill, as set forth in claim 6, wherein said hard material plate(9) has a cutting surface (11) facing in the drilling direction andforming a smooth transition with an end surface of said helical threadat said drilling head end and facing in the drilling direction.